Como no en xda han sacado el .apk del wallpaper
http://forum.xda-developers.com/showthread.php?t=872923
1. Download the Nexus S livewallpaper.apk
2. Copy the file to your SD-Card
3. Open "Root Explorer"
4. Do a backup of your "livewallpaper.apk" in "system/app"
5. Copy the Nexus S "livewallpaper.apk" to "system/app"
6. Reboot
7. Enjoy